The present invention relates to a novel process for the production of paravinyl phenol by reaction of parahydroxybenzaldehyde with malonic acid followed by decarboxylation all in one step to produce impure paravinyl phenol which is then immediately reacted with an acetylating agent to produce paraacetoxy phenol which is separated from the impurities and hydrolyzed to form food grade paravinyl phenol.
Paravinyl phenol is a highly desirable food flavoring substance. It is known to be present in natural vanilla extract and it is considered by many flavorists in the art to be the key chemical for the flavor in vanilla extract. It is also considered to be important for cocoa, cocoa butter and especially for delicate smoky notes in whiskey and roasted peanuts. In view of the presently high cost of vanilla bean, and inconsistent availability of vanilla extract, the production of food grade paravinyl phenol has become very important. Paravinyl phenol, having the structure: ##STR1## has a vanilla extract-like, cocoa butter-like, cocoa-like, roasted peanut-like and sweet aroma and taste characteristic of 0.5 ppm. Fujimaki et al, Agric. Biol. Chem., 41(9) 1721-1725, 1977, indicates that the paravinyl phenol is present as a volatile phenol in the steam distillate of rice bran. The organoleptic characteristics of paravinyl phenol are set forth in the December 1978 issue of Critical Review in Food, Science and Nutrition 10 (4) 1978 at pages 335-336. Walradt et al identified paravinyl phenol as a constituent of popcorn flavor in J. Agr. Food Chem. Volume 18, No. 5, 1970 at page 926. Paravinyl phenol has also been identified as an aroma constituent of the Cloudberry (Rubus chamaemorus L.) in a paper by Pyysalo et al, Lebensmittel-Wiffenschaft Technologie, Volume 10, (1977) at page 36.
Paravinyl phenol is also known to be useful in augmenting or enhancing the aroma or taste of perfume compositions, perfumed articles and colognes as well as smoking tobaccos and smoking tobacco articles. Thus, insofar as smoking tobacco and smoking tobacco articles are concerned, the paravinyl phenol augments or enhances the earthy, sweet, leathery and vanilla-like aromas of smoking tobaccos in general prior to smoking and on smoking it imparts a smooth, sweet, vanilla-like character to smoke flavor and enhances the body. It is one of the more compatible materials with natural tobaccos known today.
Insofar as augmenting or enhancing the aroma of perfume compositions and perfumed articles, the paravinyl phenol augments or enhances floral, animal-like, waxy aromas and aroma nuances reminiscent of ylang, jasmin, tuberose and karo-karounde. It imparts a very natural-like aroma to other synthetics and it augments or enhances other natural aroma materials.
Previous preparations of paravinyl phenol are well known in the art. Among the more efficient preparations of paravinyl phenol is that disclosed in Belgian Pat. No. 789,996 published on Apr. 12, 1973 (title: "Process for the Decarboxylation of Hydroxyarylcarboxylic Acids") at Example V where it is indicated that parahydroxybenzaldehyde may be reacted with malonic acid in the presence of dimethylformamide, ethylenediamine and benzene to form paravinyl phenol in one step. Although the process is efficient, the product obtained is contaminated with dimethylformamide and the flavor and tobacco uses of this material are nil as a result of the impossibility of separating the dimethylformamide from the paravinyl phenol. Attempts to remove the dimethylformamide by extraction proved to be impossible. Thus, the process disclosed by Belgian Pat. No. 789,996, to wit: ##STR2## has been found to be incapable of use for the purposes of production of food grade paravinyl phenol, by itself.
Corson et al in a paper entitled "Preparation of Vinylphenols and Isopropenylphenols", volume 23, April, 1958 J. Org. Chem., discribes the process for production of paravinyl phenol going through paraacetoxystyrene according to the reaction sequence: ##STR3## However, this reaction involves a complicated four step process including acylation of phenol to form paraacetyl phenol followed by acylation of the paraacetyl phenol to form paraacetoxyacetophenone followed by hydrogenation of the paraacetoxyacetophenone to form paraacetoxyhydroxyethylbenzene followed by dehydration thereof to form the paraacetoxystyrene followed by hydrolysis to form paravinyl phenol.
Nothing in the prior art, however, indicates the efficient one-step, high yield reaction using the dimethylformamide-ethylenediamine-cyclohexane reaction system followed by acylation of impure paravinyl phenol to form the paraacetoxystyrene followed by subsequent separation and hydrolysis to form food grade paravinyl phenol.
The foregoing reaction sequences and in subsequent reactions the material indicated thusly: ##STR4## is indicative of impure paravinyl phenol and the material indicated thusly: ##STR5## is indicative of food grade paravinyl phenol.
For the purposes of the disclosure herein, the parahydroxybenzaldehyde may be prepared by any process which gives rise to a substance which ultimately gives rise to the food grade paravinyl phenol. Thus, for example, the processes set forth in U.S. Pat. No. 4,195,041 issued on Mar. 25, 1980, may be used in the production of parahydroxybenzaldehyde for the purposes of this disclosure. Thus, the disclosure of U.S. Pat. No. 4,195,041 issued on Mar. 25, 1980, is herewith incorporated herein by reference.
Other publications which are indicative of the potential organoleptic uses of paravinyl phenol are as follows:
i. Walradt et al, Ag. and Food Chem., Vol. 19, 5, pages 972-9 (October 1971), indicating that paravinyl phenol is known to be present in natural peanut flavor. PA1 ii. Walradt et al, J. Agr. Food & Chem., Vol. 18, No. 5, 1970 at page 926, indicating that paravinyl phenol is a constitutent to popcorn flavor. PA1 iii. Lloyd et al, Tobacco International, 125 (Summary of CORESTA Symposium, 1974, Montreux, Switzerland) and Tobacco Science, XX: 43-51, 1976, indicating that paravinyl phenol exists in Flue-cured tobacco flavor.